|With the present study we wanted to show, whether tumor-protective effects of antidiabetics, beta-blockers and anti-inflammatory drugs on breast cancer cells are shown in vitro. The drugs metformin (7.5 and 2.5 mg / ml), propranolol (2.4 and 1.2 mg / ml), aspirin (1.0 and 0.5 mg / ml) were administered to the cell line MCF 7 (ER / PR +), BT 20 (ER / PR-), MCF 10a (ER / PR-) and MCF 12a (ER / PR +). The strongest growth-inhibiting effect was found in the beta-blocker propranolol. Metformin and ASA also inhibit growth. A cytotoxic effect was undetectable.